JP2006197440A - Antenna circuit conductor and non-contact ic tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-contact IC tag reducing the loss of an antenna circuit conductor and having the antenna circuit conductor. <P>SOLUTION: The antenna circuit conductor 2, in which a recessed section 31 is formed previously at a place, where the edge section 21 of the antenna circuit conductor 2 on the surface of a base material is formed, the recessed section 31 is filled with a conductive member by a printing method and the side face of the edge section 21 is made approximately perpendicular to the surface of the base material, is formed. Accordingly, the sectional area of the edge section 21 of the antenna circuit conductor 2, through which a high-frequency current flows, can be expanded, the loss of antenna characteristics is reduced and a thinning and a low manufacturing cost can be realized. The non-contact IC tag improving antenna characteristics can be provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna circuit conductor and a contactless IC tag.

The non-contact IC tag is composed of an antenna circuit conductor for transmitting and receiving radio waves to and from the IC chip.
There are three types of methods for manufacturing the antenna circuit conductor. One is a method in which copper or aluminum foil is pasted on an insulating substrate (flexible sheet such as glass epoxy or polyester film) and etched, The first is a winding method in which a conductor having a circular or rectangular cross section is wound in a spiral shape, and the third is a method in which a conductive paste is formed on a flexible sheet such as a polyester film by printing.

The former two methods (etching and winding) can select a material with a relatively low resistance (specific resistance of several μΩ · cm), so the characteristics of low resistance and high inductance required for antenna circuit conductors can be obtained. It is.
However, the etching method can form the antenna circuit conductor thinly and is excellent in physical properties, but has a problem that the manufacturing process is expensive because the manufacturing process is long and complicated.
The winding method is superior in physical properties and has the advantage that it can be manufactured at a relatively low cost. However, there is a limit to reducing the thickness, and the work of connecting the winding and the electronic component circuit is complicated, and automation is difficult. It has the problem of being difficult.
In contrast to these two methods, the printing method is advantageous in that it can be manufactured at low cost and can be made thin, and is optimal for a non-contact IC tag with a large amount of consumption.

  Here, there is a skin effect that cannot be ignored in the high frequency characteristics of the antenna circuit conductor. In general, when the frequency of a signal flowing through a circuit conductor increases, the signal collects on the surface of the circuit conductor. This is because there are many linkages with the magnetic flux at the center of the circuit conductor, and the counter electromotive force increases as the distance from the center increases, making it difficult for current to flow. As a result, the higher the frequency of the signal flowing through the circuit conductor, the more current is collected on the surface of the conductor. When the resistance of the antenna circuit conductor is not zero, the resistance per unit length depends on the cross-sectional area, so that the resistance increases as the area of the current flowing portion with respect to the total cross-sectional area decreases. That is, the higher the frequency of the flowing signal, the higher the resistance value of the circuit conductor.

  When the antenna circuit conductor is formed by the printing method, since the paste sags along the substrate before the conductive paste solidifies (FIGS. 2A and 2B), the cross section of the edge portion of the antenna circuit conductor is It becomes an acute angle shape. In such an antenna circuit conductor, particularly when a high frequency such as 2.45 GHz is handled, there is a problem that current concentrates on a portion where the cross-sectional area of the tip of the edge portion is very small and the loss increases due to the skin effect. is there.

The known literature is shown below.
JP-A-9-1970

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a non-contact IC tag having an antenna circuit conductor having a reduced loss by improving the end shape.

  In order to solve the above problems, the present invention provides an antenna circuit conductor formed of a conductive member on a substrate surface, wherein the side surface of the edge portion is substantially perpendicular to the substrate surface. It is an antenna circuit conductor characterized by the following.

  Invention of Claim 2 WHEREIN: In said antenna circuit conductor, a recessed part is previously formed in the position where the edge part of the said antenna circuit conductor of the said base-material surface is installed, The said electroconductive member is filled in the said recessed part, The antenna circuit conductor is characterized in that a side surface of the edge portion is substantially perpendicular to a surface of the substrate.

  According to a third aspect of the present invention, in the antenna circuit conductor described above, the conductive member is a conductive paste, and is formed on a film-like substrate surface by coating by a printing method. It is.

  The invention of claim 4 is a non-contact IC tag comprising an IC chip, a base material, and the antenna circuit conductor according to any one of claims 1 to 3 formed on the surface of the base material. is there.

  According to the present invention, it is possible to suppress the cross section of the antenna circuit conductor end portion from becoming an acute angle, thereby reducing the resistance by enlarging the cross-sectional area through which the high-frequency current flows, and reducing the loss of antenna characteristics. Is done. Thereby, the subject at the time of forming an antenna circuit conductor with a printing method can be solved, and thickness reduction and cheap manufacturing cost can be obtained. Furthermore, a non-contact IC tag with improved antenna characteristics can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 shows an antenna substrate 4 of the present embodiment.
The antenna substrate 4 includes a base material 3, an IC chip 1 installed on the base material 3, and a pair of antenna circuit conductors 2.
The base material 3 has a substantially rectangular shape in plan, and for example, a resin material such as polyethylene terephthalate, polycarbonate, polyimide, or paper can be used. In addition, the material of the base material 3 is not specifically limited to these.

The IC chip 1 is installed at the approximate center of the surface of the substrate 3.
A concave portion 31 having a substantially rectangular cross section is formed on the surface of the base material 3 along the longitudinal direction of the base material 3. The concave portion 31 can be formed by various surface treatments as necessary, for example, embossing, oxidation etching treatment by plasma or ultraviolet rays, and the like.

The antenna circuit conductor 2 is formed by applying a conductive paste on the substrate 3 by silk screen printing. In addition to the metal particles for showing conductivity, the conductive paste is blended with various resins such as phenol, epoxy, polyester and urethane and a diluent solvent in order to maintain adhesion with the substrate. You can use what you have.
The antenna circuit conductor 2 has a substantially rectangular shape on a plane, and is arranged so that the IC chip 1 is sandwiched between the surfaces of the base material 3. The end of the antenna circuit conductor 2 in the longitudinal direction is connected to the IC chip 1.

The conductive paste constituting the edge portion 21 of the antenna circuit conductor 2 (the end portion in the short side direction of the antenna circuit conductor 2) is filled in the concave portion 31 of the base material 3, and the side surface of the edge portion 21 is It is substantially perpendicular to the surface of the substrate 3.
The substantially perpendicular is preferably an angle of 70 degrees to 120 degrees with respect to the surface of the substrate 3.

Such an antenna substrate 4 is formed as follows.
As shown in FIG. 3A, the conductive paste is printed on the substrate 3. In order to improve the adhesion to the conductive paste, it is preferable that the substrate is previously subjected to activation treatment such as corona discharge treatment, plasma treatment, sandblast treatment, and primer treatment.
The conductive paste immediately after printing shows a shape in which the end portion stands substantially vertically, but since it has a predetermined viscosity, sagging occurs over time. However, as shown in FIG. 3 (b), the sagging conductive paste is filled in the recess 31 formed in the base material 3 to prevent spreading and the end cross section of the antenna circuit conductor 2 has an acute angle. It is suppressed.

  After the conductive paste is dried, the IC chip 1 is mounted and connected on the substrate 3 via a conductive adhesive or an anisotropic conductive adhesive film. Thus, the antenna substrate 4 can be obtained.

Example 1
FIG. 4A shows a cross-sectional view and a resistance value simulation result in an embodiment of the antenna circuit conductor used in the present invention. An antenna circuit conductor thickness is 20 μm, an antenna circuit having a rectangular recess having a width of 20 μm and a depth of 5 μm is formed on a base material. The resistance was measured when a current of 1 A was passed through a 1 m long conductor at a frequency of 2.45 GHz at a rate of 3.2.
As a result of measurement, the resistance value was 136.48 Ω / m.

(Example 2)
FIG. 4B shows a cross-sectional view and a resistance value simulation result in an embodiment of the antenna circuit conductor used in the present invention. An antenna circuit conductor thickness is 20 μm, an antenna circuit having a wedge-shaped recess having a depth of 5 μm is formed on a substrate, the conductivity of the conductive paste is 3 mS / m, and the dielectric constant assuming polyethylene terephthalate as the substrate material is 3. The resistance value was measured when a current of 1 A was passed through a 1 m long conductor at a frequency of 2.45 GHz.
As a result of measurement, the resistance value was 136.79 Ω / m.

(Comparative example)
FIG. 4C shows a cross-sectional view and a resistance value simulation result of a conventional antenna circuit conductor as a comparative example for the first and second embodiments. An antenna circuit conductor thickness is 20 μm, an antenna circuit having a rectangular recess having a width of 20 μm and a depth of 5 μm is formed on a base material, the conductivity of the conductive paste is 3 mS / m, and the dielectric material assuming polyethylene terephthalate as the base material The resistance was measured when a current of 1 A was passed through a 1 m long conductor at a frequency of 2.45 GHz at a rate of 3.2.
As a result of measurement, the resistance value was 183.84 Ω / m.

  In each of Examples 1 and 2, the loss was reduced by about 25% compared to the result of the conventional antenna circuit conductor.

In the present invention, only an example using antenna circuit conductors arranged on a straight line has been described. However, the present invention is not limited to this, and the present invention is also applied to a similar antenna having an antenna function such as a loop shape. It is possible to apply.
In the present invention, only an example using a frequency of 2.45 GHz has been described. However, the present invention is not limited to this, and the present invention can be applied to other frequency regions.

  Furthermore, in this invention, although the edge part 21 of the electrically conductive paste apply | coated by the recessed part 31 of the base material 3 was made substantially perpendicular with respect to the surface of the base material 3, the antenna circuit conductor formed by the conventional printing method was used. The edge portion may be substantially perpendicular to the substrate surface by a method of physically cutting.

  Further, in the present invention, only an example in which the antenna circuit conductor is formed by applying a conductive paste to the surface of the equipment by a silk screen printing method has been described. The present invention can be applied to edge shapes.

(A) is a schematic view of an antenna substrate having an antenna circuit conductor according to the present invention, and (b) is a cross-sectional view of the antenna substrate. (A) Cross-sectional view of antenna circuit conductor immediately after printing by conventional printing method, (b) Cross-sectional view of antenna circuit conductor in a state where conductive paste is sag by conventional printing method (A) is a cross-sectional view of an antenna circuit conductor immediately after printing according to the present invention, (b) a cross-sectional view of the antenna circuit conductor in a state in which the conductive paste according to the present invention is sagging. (A) is a simulation diagram of resistance value according to the first embodiment of the present invention, (b) is a simulation diagram of resistance value according to the second embodiment of the present invention, and (c) is a simulation diagram of resistance value according to the conventional printing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... IC chip 2 ... Antenna circuit conductor 21 ... Edge part 3 ... Base material 31 ... Concave part 4 ... Antenna circuit board

Claims (4)

An antenna circuit conductor formed of a conductive member on a substrate surface,
An antenna circuit conductor, wherein a side surface of an edge portion is substantially perpendicular to the surface of the substrate. The antenna circuit conductor according to claim 1,
A concave portion is formed in advance at a position where the edge portion of the antenna circuit conductor on the surface of the base material is installed, the conductive member is filled in the concave portion, and a side surface of the edge portion is substantially perpendicular to the base material surface. An antenna circuit conductor characterized by: The antenna circuit conductor according to claim 1 or 2,
The antenna circuit conductor according to claim 1, wherein the conductive member is a conductive paste, and is formed on a surface of a film-like base material by application by a printing method. An IC chip, a substrate,
A non-contact IC tag comprising the antenna circuit conductor according to claim 1 formed on the surface of the substrate.